Fields phase expands lazy vals like modules

They remain ValDefs until then.

- remove lazy accessor logic
  now that we have a single ValDef for lazy vals,
  with the underlying machinery being hidden until the fields phase
  leave a `@deprecated def lazyAccessor` for scala-refactoring

- don't skolemize in purely synthetic getters,
  but *do* skolemize in lazy accessor during typers

  Lazy accessors have arbitrary user code, so have to skolemize.
  We exempt the purely synthetic accessors (`isSyntheticAccessor`)
  for strict vals, and lazy accessors emitted by the fields phase
  to avoid spurious type mismatches due to issues with existentials
  (That bug is tracked as https://github.com/scala/scala-dev/issues/165)

  When we're past typer, lazy accessors are synthetic,
  but before they are user-defined to make this hack less hacky,
  we could rework our flag usage to allow for
  requiring both the ACCESSOR and the SYNTHETIC bits
  to identify synthetic accessors and trigger the exemption.

  see also https://github.com/scala/scala-dev/issues/165

  ok 7 - pos/existentials-harmful.scala
  ok 8 - pos/t2435.scala
  ok 9 - pos/existentials.scala

  previous attempt: skolemize type of val inside the private[this] val

  because its type is only observed from inside the
  accessor methods (inside the method scope its existentials are skolemized)

- bean accessors have regular method types, not nullary method types

- must re-infer type for param accessor
  some weirdness with scoping of param accessor vals and defs?

- tailcalls detect lazy vals, which are defdefs after fields

- can inline constant lazy val from trait

- don't mix in fields etc for an overridden lazy val

- need try-lift in lazy vals: the assign is not seen in uncurry
  because fields does the transform (see run/t2333.scala)

- ensure field members end up final in bytecode

- implicit class companion method: annot filter in completer

- update check: previous error message was tangled up with unrelated
  field definitions (`var s` and `val s_scope`),
  now it behaves consistently whether those are val/vars or defs

- analyzer plugin check update seems benign, but no way to know...

- error message gen: there is no underlying symbol for a deferred var
  look for missing getter/setter instead

- avoid retypechecking valdefs while duplicating for specialize
  see pos/spec-private

- Scaladoc uniformly looks to field/accessor symbol

- test updates to innerClassAttribute by Lukas

1 files changed, 25 insertions, 26 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index a95ecd360c..3360599c1b 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -128,6 +128,15 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
     def canTranslateEmptyListToNil    = true
     def missingSelectErrorTree(tree: Tree, qual: Tree, name: Name): Tree = tree
 
+    // used to exempt synthetic accessors (i.e. those that are synthesized by the compiler to access a field)
+    // from skolemization because there's a weird bug that causes spurious type mismatches
+    // (it seems to have something to do with existential abstraction over values
+    // https://github.com/scala/scala-dev/issues/165
+    // when we're past typer, lazy accessors are synthetic, but before they are user-defined
+    // to make this hack less hacky, we could rework our flag assignment to allow for
+    // requiring both the ACCESSOR and the SYNTHETIC bits to trigger the exemption
+    private def isSyntheticAccessor(sym: Symbol) = sym.isAccessor && (!sym.isLazy || isPastTyper)
+
     // when type checking during erasure, generate erased types in spots that aren't transformed by erasure
     // (it erases in TypeTrees, but not in, e.g., the type a Function node)
     def phasedAppliedType(sym: Symbol, args: List[Type]) = {
@@ -1159,7 +1168,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           adapt(tree setType restpe, mode, pt, original)
         case TypeRef(_, ByNameParamClass, arg :: Nil) if mode.inExprMode => // (2)
           adapt(tree setType arg, mode, pt, original)
-        case tp if mode.typingExprNotLhs && isExistentialType(tp) =>
+        case tp if mode.typingExprNotLhs && isExistentialType(tp) && !isSyntheticAccessor(context.owner) =>
           adapt(tree setType tp.dealias.skolemizeExistential(context.owner, tree), mode, pt, original)
         case PolyType(tparams, restpe) if mode.inNone(TAPPmode | PATTERNmode) && !context.inTypeConstructorAllowed => // (3)
           // assert((mode & HKmode) == 0) //@M a PolyType in HKmode represents an anonymous type function,
@@ -1373,13 +1382,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
               notAllowed(s"redefinition of $name method. See SIP-15, criterion 4.")
             else if (stat.symbol != null && stat.symbol.isParamAccessor)
               notAllowed("additional parameter")
-            // concrete accessor (getter) in trait corresponds to a field definition (neg/anytrait.scala)
-            // TODO: only reject accessors that actually give rise to field (e.g., a constant-type val is fine)
-            else if (!isValueClass && stat.symbol.isAccessor && !stat.symbol.isDeferred)
-              notAllowed("field definition")
             checkEphemeralDeep.traverse(rhs)
-          // for value class or "exotic" vals in traits
-          // (traits don't receive ValDefs for regular vals until fields phase -- well, except for early initialized/lazy vals)
           case _: ValDef =>
             notAllowed("field definition")
           case _: ModuleDef =>
@@ -1956,11 +1959,8 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
       if (!phase.erasedTypes && !clazz.info.resultType.isError) // @S: prevent crash for duplicated type members
         checkFinitary(clazz.info.resultType.asInstanceOf[ClassInfoType])
 
-      val body2 = {
-        val body2 =
-          if (isPastTyper || reporter.hasErrors) body1
-          else body1 flatMap rewrappingWrapperTrees(namer.addDerivedTrees(Typer.this, _))
-        val primaryCtor = treeInfo.firstConstructor(body2)
+      val bodyWithPrimaryCtor = {
+        val primaryCtor = treeInfo.firstConstructor(body1)
         val primaryCtor1 = primaryCtor match {
           case DefDef(_, _, _, _, _, Block(earlyVals :+ global.pendingSuperCall, unit)) =>
             val argss = superArgs(parents1.head) getOrElse Nil
@@ -1969,10 +1969,10 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
             deriveDefDef(primaryCtor)(block => Block(earlyVals :+ superCall, unit) setPos pos) setPos pos
           case _ => primaryCtor
         }
-        body2 mapConserve { case `primaryCtor` => primaryCtor1; case stat => stat }
+        body1 mapConserve { case `primaryCtor` => primaryCtor1; case stat => stat }
       }
 
-      val body3 = typedStats(body2, templ.symbol)
+      val body3 = typedStats(bodyWithPrimaryCtor, templ.symbol)
 
       if (clazz.info.firstParent.typeSymbol == AnyValClass)
         validateDerivedValueClass(clazz, body3)
@@ -2436,13 +2436,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
             case _ =>
           }
         }
-        val stats1 = if (isPastTyper) block.stats else
-          block.stats.flatMap {
-            case vd@ValDef(_, _, _, _) if vd.symbol.isLazy =>
-              namer.addDerivedTrees(Typer.this, vd)
-            case stat => stat::Nil
-          }
-        val stats2 = typedStats(stats1, context.owner, warnPure = false)
+        val statsTyped = typedStats(block.stats, context.owner, warnPure = false)
         val expr1 = typed(block.expr, mode &~ (FUNmode | QUALmode), pt)
 
         // sanity check block for unintended expr placement
@@ -2456,18 +2450,18 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           def checkPure(t: Tree, supple: Boolean): Unit =
             if (treeInfo.isPureExprForWarningPurposes(t)) {
               val msg = "a pure expression does nothing in statement position"
-              val parens = if (stats2.length + count > 1) "multiline expressions might require enclosing parentheses" else ""
+              val parens = if (statsTyped.length + count > 1) "multiline expressions might require enclosing parentheses" else ""
               val discard = if (adapted) "; a value can be silently discarded when Unit is expected" else ""
               val text =
                 if (supple) s"${parens}${discard}"
                 else if (!parens.isEmpty) s"${msg}; ${parens}" else msg
               context.warning(t.pos, text)
             }
-          stats2.foreach(checkPure(_, supple = false))
+          statsTyped.foreach(checkPure(_, supple = false))
           if (result0.nonEmpty) checkPure(result0, supple = true)
         }
 
-        treeCopy.Block(block, stats2, expr1)
+        treeCopy.Block(block, statsTyped, expr1)
           .setType(if (treeInfo.isExprSafeToInline(block)) expr1.tpe else expr1.tpe.deconst)
       } finally {
         // enable escaping privates checking from the outside and recycle
@@ -3171,6 +3165,10 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
             case (ClassDef(cmods, cname, _, _), DefDef(dmods, dname, _, _, _, _)) =>
               cmods.isImplicit && dmods.isImplicit && cname.toTermName == dname
 
+            // ValDef and Accessor
+            case (ValDef(_, cname, _, _), DefDef(_, dname, _, _, _, _)) =>
+              cname.getterName == dname.getterName
+
             case _ => false
           }
 
@@ -4455,8 +4453,9 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         def narrowRhs(tp: Type) = { val sym = context.tree.symbol
           context.tree match {
             case ValDef(mods, _, _, Apply(Select(`tree`, _), _)) if !mods.isMutable && sym != null && sym != NoSymbol =>
-              val sym1 = if (sym.owner.isClass && sym.getterIn(sym.owner) != NoSymbol) sym.getterIn(sym.owner)
-                else sym.lazyAccessorOrSelf
+              val sym1 =
+                if (sym.owner.isClass && sym.getterIn(sym.owner) != NoSymbol) sym.getterIn(sym.owner)
+                else sym
               val pre = if (sym1.owner.isClass) sym1.owner.thisType else NoPrefix
               intersectionType(List(tp, singleType(pre, sym1)))
             case _ => tp